1. Field of the Invention
The present invention relates to NKT cell-activating agents, therapeutic agents for autoimmune diseases and agents for inducing abortion.
2. Background Art
It has been revealed that intermediate TCR cells (TCRint cells), which express T-cell receptors (TCRs) intermediately, are related to natural killer (NK) cells in terms of their features, for example, showing a large granular lymphocyte (LGL) -like morphology, constantly expressing IL-2R xcex2-chains, and having perforin granules, but they are clearly different from NK cells in terms of having TCRs (Watanabe, H. et al., J. Immunol., 155, 2972 (1995)). Furthermore, among the TCRint cells activated by interleukin 12 (IL-12), NK 1.1-expressing NK 1.1+TCRint (NKT) cells have been shown to be important effector cells in controlling hematogenous metastases of tumors to the liver and lung in mice (Hashimoto, W. et al., J. Immunol., 154, 4333 (1995); Anzai, R. et al., Immunol., 88, 82 (1996)). These data suggest that the NKT cells may play an important role in eradicating cancer cells, parasites, protozoans, and intracellular infectious bacteria such as Listeria monocytogenes and Micobacterium tubeculosis (Seki, S. et al., Clin. Immunol., 28, 1069 (1996)).
The NKT cells are also known to be closely associated with acute rejection in bone marrow transplantation (Yankelevich, B. et al., J. Immunol., 142, 3423 (1989)) and with controlling of IgE antibody production by controlling Th1/Th2 differentiation of helper T cells (Yoshimoto, T. et al., J. Exp. Med., 179, 1285 (1994)). Thus, the NKT cells are a group of new cells that are currently attracting enormous attention.
Vxcex114+ NKT cells are a subset of the above-mentioned NKT cells. Many Vxcex114+ NKT cells express Vxcex114Jxcex1281 mRNA and have this as a TCR xcex1-chain. Recently, the Vxcex114+ NKT cells were shown to be closely associated with the onset of autoimmune diseases. The number of Vxcex114+ NKT cells was revealed to selectively decrease prior to the onset of an autoimmune disease in MRL lpr/lpr mice, model mice for an autoimmune disease (human systemic lupus erythematosus) in which abnormal lymphocytes accumulate at 17-20 weeks old (Mieza, M. A. et al., J. Immunol., 156, 4035 (1996)).
Similar phenomena were also observed in model mice for other autoimmune diseases, such as gld mice and (NZBxNZW) F1 mice, revealing that the Vxcex114+ NKT cells are closely associated with the onset of autoimmune diseases (Makino, Y. et al., Clin. Immunol., 28, 1487 (1996)).
More interestingly, similar phenomena were also observed in humans. The Vxcex124Jxcex1Qxcex1 chain, a human homologue to the mouse Vxcex114Jxcex1281 chain, was found in peripheral blood CD4xe2x88x92/CD8xe2x88x92 T cells at a level of 20-50% in healthy humans but not at all in sclerosis patients (Sumida, T. et al., J. Exp. Med., 182, 1163 (1995)).
Thus, the mouse Vxcex114+ NKT cells and human Vxcex124Jxcex1Qxcex1 T cells are known to be involved in various autoimmune diseases which are caused by different causative genes or genetic background. Therefore, IL-12 having an NKT cell-activating activity as mentioned above was expected to be a therapeutic agent for autoimmune diseases such as human systemic lupus erythematosus (SLE) and systemic sclerosis (SSc). However, a marked increase in the number of abnormal lymphocytes (CD3+B220+ double negative T cells) in the spleen and lymph nodes was observed in MRL lpr/lpr mice to which IL-12 was administered as compared with the control mice (Takenori Tsutsui et al., Proceedings of Annual Meeting of the Japanese Society for Immunology, 347 (1996)).
xcex2-Galactosylceramides or xcex2-glucosylceramides, in which various sugars bound to ceramides in a xcex2-configuration, are present in the mammal body (Svennerholm, L. et al., Biochim. Biophys. Acta, 280, 626 (1972); Karlsson, K. -A. et al., Biochim. Biophys. Acta, 316, 317 (1973)). On the other hand, it is known that xcex1-galactosylceramides have marked immunostimulatory activity and antitumor activity (Morita, M. et al., J. Med. Chem., 38, 2176 (1995)) and such activities by xcex1-galactosylceramides or xcex1-glucosylceramides are known to be much stronger than those by xcex2-galactosylceramides or xcex2-glucosylceramides (Motoki, K. et al., Biol. Pharm. Bull., 18, 1487 (1995)). It is also known that administration of compounds having an xcex1-glucosylceramide structure protects the bodyfrom radiation (Motoki, K. etal., Bioorg. Med. Chem. Lett., 5, 2413 (1995)), suppresses the metastasis of mouse melanoma B16 to the lung (Kobayashi, E. et al., Oncology Res., 7, 529 (1995)) and metastasis of mouse colon adenocarcinoma, Colon 26, and mouse T lymphoma EL-4 to the liver (Kazuhiro Motoki et al., Proceedings of Annual Meeting of the Japanese Cancer Association, 523 (1996)), and increases the number of platelets and leukocytes (Motoki, K. et al., Biol. Pharm. Bull., 19, 952 (1996)).
However, there are no reports to date that compounds having an xcex1-glucosylceramide structure are effective on autoimmune diseases, that such compounds would induce abortion, or that such compounds could even affect NKT cells.
The present inventors have now found that xcex1-glycosylceramides enhance antitumor cytotoxic activity against tumor cells of NKT cells in RAG-1KO/Vxcex114tg/Vxcex28.2tg mice (mice having a large number of NKT cells but neither B cells, T cells nor NK cells in the lymphocyte fraction), markedly increase the number of NKT cells, in particular, mouse Vxcex114+ NKT cells and human Vxcex124+ NKT cells, suppress abnormal swelling of axillary and inguinal lymph nodes (accumulation of abnormal lymphocytes) in MRL lpr/lpr mice which are considered model mice for human systemic lupus erythematosus, and control the progression of mouse colitis induced with 4% DSS. The present inventors have also found that xcex1-glycosylceramides suppress the onset of experimental autoimmune encephalomyelitis. This experimental autoimmune encephalomyelitis in mice is a model for human multiple sclerosis. The present inventors have also found that xcex1-glycosylceramides suppress the spontaneous onset of diabetes in NOD mice which are model animals for human type I diabetes.
The present inventors have further found that xcex1-glycosylceramides have an aborting effect on pregnant mice.
An objective of the present invention is to provide an agent for activating an NKT cell and an activated NKT cell.
Another objective of the present invention is to provide a therapeutic agent for autoimmune diseases such as systemic lupus erythematosus, systemic sclerosis, ulcerative colitis, encephalomyelitis, multiple sclerosis, or type I diabetes.
Further objective of the present invention is to provide an agent for inducing abortion.
The NKT cell-activating agent, the therapeutic agent for autoimmune diseases and the agent for inducing abortion according to the present invention comprise a compound of formula (I) or a salt or a solvate thereof: 
wherein
R1 represents H or OH,
X represents an integer between 7 and 27,
R2represents a substituent selected from the group consisting of the following (a) to (e) (wherein Y represents an integer between 5 and 17):
(a) xe2x80x94CH2(CH2)yCH3 
(b) xe2x80x94CH(OH)(CH2)yCH3 
(c) xe2x80x94CH(OH)(CH2)yCH(CH3)2 
(d) xe2x80x94CHxe2x95x90CH(CH2)yCH3 
(e) xe2x80x94CH(OH)(CH2)yCH(CH3)CH2CH3, and
R3 to R9 represent substituents as defined in any one of the following i) to ii):
i) when R3, R6 and R8 represent H,
R4 represents H, OH, NH2, NHCOCH3, or a substituent selected from the group consisting of the following groups (A) to (D): 
R5represents OH or a substituent selected from the group consisting of the following groups (E) and (F): 
R7represents OH or a substituent selected from the group consisting of the following groups (A) to (D): 
R9 represents H, CH3, CH2OH or a substituent selected from the group consisting of the following groups (Axe2x80x2) to (Dxe2x80x2): 
ii) when R3, R6 and R7 represent H,
R4 represents H, OH, NH2, NHCOCH3, or a substituent selected from the group consisting of the following groups (A) to (D): 
R5 represents OH or a substituent selected from the group consisting of groups (E) and (F): 
R8 represents OH or a substituent selected from the group consisting of the following groups (A) to (D): 
R9 represents H, CH3, CH2OH or a substituent selected from the group consisting of the following groups (Axe2x80x2) to (Dxe2x80x2): 